When a virtual machine is deployed in a data center, a thin client uses a remote desktop protocol to access the virtual machine. A soft phone computer program can be deployed on such a virtual machine, and the thin client can be configured to provide a user control interface, as well as terminate incoming voice and video streams, and generate outgoing voice and video streams. Local virtual device drivers in the thin client device are used to render incoming audio and video, and to capture the outgoing audio and video. The remote desktop protocol provides the control of voice and video data between the virtual machine and the thin client system that sits with the employee using the desktop. Improvements in this protocol can optimize the transmission of real time voice and video as perceived by the user between the virtual machine and the thin client. In addition, improvements have been developed that create a SIP back to back capability in a virtual desktop infrastructure system. However, where a thin client handles both SIP protocol communications and other media streams that are routed through the virtual machine, there is the possibility of media contention issues at the thin client.